The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft nacelle is designed to encase a turbojet engine and produce the thrust of the turbojet engine by channelling the flows generated by the engine. It must also be possible to open said nacelle to access the engine and its equipment.
Most turbojet nacelles comprise a fan cowl which encases the engine fan casing and a rear body (often a thrust reverser) which encases the central part of the engine.
To provide access to the engine and its equipment, both nacelle components generally open into two halves.
Said doors or cowls can be opened by means of hinges, usually mounted on the upper part of the nacelle, in a so-called twelve o'clock position, along a mast line, and are held closed by a plurality of locks mounted generally along a locking line on the lower part of the nacelle in a so-called six o'clock position.
It is understandably essential to close all locks after every maintenance operation.
To this end, all removable cowls of a nacelle must be efficiently, safely and rapidly locked before a nacelle is put into operation. Currently, this safety check depends in most cases almost entirely on the vigilance of the mechanic who carries out the locking operation. As a result, maintenance errors have caused a significant number of faulty closures of fan cowls, sometimes causing major in-flight events, (opening and loss of fan cowl). A clear indicator signalling that the nacelle cowl is locked will be a source of significant improvement in flight safety.
One of the most frequent causes of inflight openings is the partial opening or closing of the cowl latches. In this case, it is often difficult to notice that one or more latches are not properly closed during a routine check, because locking a single latch “secures” the cowl, which then seem to be properly closed when seen from a distance.
Thus, to provide an efficient detection system, it must be impossible to start unlocking or partially unlock the cowl without a corresponding status indicator displays an unlock status.
Of course, such considerations also apply to nacelles which are not fitted with thrust reversers, known as smooth nacelles, and which comprise movable cowls to access the nacelles in the same way, and also to other maintenance cowls equipping the nacelle.
There is therefore a need for a closure detecting system which meets the above-mentioned requirements.
Such electrical locking detection systems making it possible to perform a visual control of the situation are well-known. However, such systems require a power supply source and are subject to possible electrical faults.
However, one of the difficulties associated with a mechanical system lies in providing that the unlocking indicator displays clearly an unlock status when a first latch is opened and, conversely, that said indicator does not switch to the lock status unless strictly all latches are locked.
Moreover, the existing mechanical systems only monitor the position of the latch handle, while the desired mechanical function is that of pressing the latches.
To this end, Document FR 2 966 488 discloses a device for locking between a first structure and a second structure comprising at least one locking pair comprising at least one bolt linked to the first structure and adapted to engage with at least one corresponding retaining means, linked to the second structure, the bolt being further mounted movable against at least one elastic return means that tends to return it in a position spaced apart from the retaining means,
said locking device comprising at least one detection linkage, movably mounted between a first position wherein it makes it possible to unlock the bolt and the retaining means, at least a part of the bolt then engaging with the linkage to block a possible return of said linkage to a second position, and said second position wherein the linkage engages with at least a part of the locking pair to block the unlocking thereof.
By providing a linkage blocked in position by the bolt when the locking pair is unlocked, the linkage cannot return to its second position, indicating that the device is locked, unless the locking pair is actually relocked. In the case of a plurality of locking pairs with linkages connected together, said linkages cannot return to their second position indicating that the associated locking pair is relocked unless all locking pairs have been relocked.
Conversely, for the unlocking operation, by providing a linkage element engaging with part of a locking pair to block the unlocking of said pair, it is necessary to switch the linkage to its first position, thus indicating the unlocking, to effectively unlock the locking pair.
Thus, with such a device, a status indicator associated with the linkage will always indicate the status of the locking pairs and block any status change that is not passed on to said status indicator.
Implementation and development studies have shown that several aspects of this locking system could still be improved.
The preceding device provides in particular that the indicator, and more generally the associated linkage, must be switched to the unlocking position to effectively unlock the latches.
This can be a source of potential annoyance for the operator during maneuverings.